A transmission apparatus, such the L2 switch, performs a variety of processes including a rewrite process of a packet, or a forwarding process, by saving a received packet on a memory, and performing read-write control on the packet stored on the memory. For example, communication traffic volume has been drastically increasing as smart phones or tablet terminals are in widespread use or a variety of network services becomes available. As a result, the capacity of a memory used in a large scale integration (LSI) or a field programmable gate array (FPGA) in transmission apparatuses tends to increase. With a higher memory capacity, an occurrence rate of memory error, such as a single event upset or a physical fault is increasing accordingly.
If a memory error occurs on a large-size and high-rate packet, the transmission apparatus suffers from a pronounced effect, such as a packet loss and communication interruption. For this reason, even while the transmission apparatus is active in service, the fault diagnosis is performed to quickly detect a memory error. Related art techniques are disclosed in Japanese Laid-open Patent Publication No. 2009-296320 and Japanese Laid-open Patent Publication No. 5-236562.
FIG. 13A illustrates an example of a fault diagnosis timing. FIG. 13B illustrates another example of the fault diagnosis timing. A transmission apparatus performs a fault diagnosis 303 on an internal memory thereof during an idle time duration 302 between a memory control operation 301 and another memory control operation 301 as illustrated in FIG. 13A while performing memory control, such as read and write operations on the internal memory. As a result, the transmission apparatus performs the fault diagnosis during the system operation.
The transmission apparatus receives data without interruption as illustrated in FIG. 13B since data is handled in a larger amount at a higher rate. With the idle time duration 302 difficult to insert between the memory control operations 301, the fault diagnosis 303 is not performed. For this reason, the fault diagnosis is desirably performed in active operation.